A Second World War underground wireless station in Norwich, which was part of a secret communications network set up in 1940 by Churchill in response to the increasing threat of German invasion, has been protected as a scheduled monument by the Department for Culture, Media and Sport on the advice of Historic England.

Discovered in 2012 by a retired groundsman in the gardens of a Norwich country house, this wireless station, also known as an IN-Station or Zero Station, is thought to be one of just 32 built in England during the Second World War.

Only 12 have been found and this is one of the most intact examples discovered so far, complete with a fake bookcase to conceal the wireless room and an escape tunnel.

Secret civilian army

By June 1940 the increasing threat of German invasion and potential occupation prompted Winston Churchill to set up a secret army unit called GHQ Auxillary Units with a particular branch known as “Special Duties”.

This branch was made up of civilian volunteers living in the most threatened coastal areas in the country, trained to spy and report on German military activities from within occupied areas.

The recruits in “Churchill’s Secret Army”, also known as the “British Resistance Organisation”, had to verbally swear to secrecy, with one hand on a Bible. In some cases even their families knew nothing of the role that required them to leave their homes regularly at night.

These civilian spies communicated with the army by a secret wireless network. Messages were transmitted from OUT-Stations in enemy occupied areas to IN-Stations, like this one, which were outside the occupied area and manned by the military, usually female Auxillary Territorial Service officers.

Heritage Minister David Evennett said: "This underground wireless station is a rare and unusual example of our Second World War heritage and deserves to be protected. It is a reminder too of the often forgotten role so many civilians played in the war effort often acting in secret and undercover."

Historic England’s Tony Calladine said: “This amazing place that has survived intact played a highly secret but vitally important role in preparing us for a feared invasion during the Second World War. Because so much information about the stations was either hidden or destroyed, this small but significant dugout has great potential to teach us about a relatively little known area of our 20th century military history.”

The unfolding mystery

In July 1944 3,500 civilians had been trained and over 125 civilian-run OUT-Stations had been established, often hidden in dugouts or behind dummy walls in houses. In this same month the “Special Duties” branch was closed down, equipment stripped from the stations and their entrances hidden.

Details about their locations and construction were kept secret and very little documentation of the stations exists. Information was protected in case they should be needed again in the future.

Historic England is asking the public to come forward with information about family members who were trained to be a civilian spies, or any clues as to where the remaining 20 IN-stations lay hidden.